JPS61155292A - Vapor growth device - Google Patents

Abstract

PURPOSE:To prevent formation of crystals on a wall surface of a reaction tube between a supporting bed and an introducing port of a sample by providing an introducing port of inert gas and a discharging port of the starting material gas and the inert gas. CONSTITUTION:A crystal substrate 8 is placed through a sample introducing port 3 on a supporting bed 4 provided in a reaction tube 1, and the neighborhood of the substrate 8 is heated by a high frequency coil 7. On one hand, starting material gas is fed into the reaction tube 1 through an inlets 2 of the reaction tube and decomposed thermally at the neighborhood of the substrate to cause epitaxial growth on the surface of the substrate 8. Simultaneously, inactive gas for the reaction is introduced through an introducing port 5 of gas and the starting material gas having passed the reaction zone near the substrate 8 is discharged from a gas discharging port 6. By this method, defects on the crystal surface which have been ca. 1,000/cm<2> by a conventional method, are reduced to 100-500/cm<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a vapor phase growth apparatus, and more particularly to a vapor phase growth apparatus used in the manufacture of semiconductor elements.

[Prior art and its problems]

Thin film growth is an extremely important step in producing semiconductor devices with fine structures such as highly integrated circuits, 1'-conductor lasers, and photodetectors. Vapor-phase epitaxy, liquid-phase epitaxy, and molecular beam epitaxy are used as thin film growth methods, but vapor-phase epitaxy has the advantage of direct growth from raw material gas to a crystal substrate, making it suitable for mass production. The best in the city.

In a conventional vapor phase growth apparatus using the vapor phase deposition method, the raw material gas is passed through a gas pump, or in the case of liquid raw material, it is passed through a bubbler.
hler) to the reaction tube together with the transport gas. The crystal substrate is heated in the reaction tube by resistance heating, high frequency heating, etc., and the raw material gas sent is heated to the crystal substrate.
A chemical reaction occurs at or near the crystal substrate and epitaxial growth occurs on the crystal substrate.

The crystal substrate is introduced into the reaction tube at room temperature, and growth is started only after gas exchange within the reaction tube and temperature rise of the reaction tube are completed and growth conditions are established. In such a state, in a conventional vapor phase growth apparatus, for example, l.trimethylgallium (tr
imethyle gallium) and arsine (A
In the case of crystal growth of the ■-■ group using rsine), arsenic and gallium arsenic produced on the reaction tube wall during the previous growth fall onto the substrate surface and adhere to the surface when the substrate is loaded and unloaded. This has the disadvantage of worsening the surface condition of the m-film crystal. Therefore, a countermeasure has been taken to wash the reaction tube after each crystal growth, but at this time, moisture and air are introduced into the reaction tube, which causes a new problem in that the electrical characteristics of the grown crystal become unstable. was.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned drawbacks and problems by devising the structure of the reaction tube, and to provide a vapor phase growth apparatus that can improve the condition of the crystal surface.

[Structure of the invention]

The present invention provides a vapor phase growth apparatus equipped with a reaction tube having an inlet for supplying a raw material gas, a sample introduction port for mounting and taking out a substrate, and a support stand for arranging a substrate, in which the reaction tube is connected to the raw material gas. A gas inlet for feeding an inert gas into the reaction and a gas outlet for discharging the raw material gas and the inert gas are provided downstream from the support stand to the sample inlet with respect to the gas flow. The present invention is characterized in that crystals are not generated on the wall of the reaction tube between the gas outlet and the sample inlet.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of, for example, a gallium arsenide vapor phase growth apparatus which is an embodiment of the vapor phase growth apparatus of the present invention.

This vapor phase growth apparatus is equipped with a quartz reaction tube 1, and this quartz reaction tube 1 has a reaction tube 2 for feeding raw material gas, and a sample located downstream of the gas flow for mounting and taking out a crystal substrate. In the reaction tube 1, a graphite support 4 for placing a crystal substrate is provided. Further, the quartz reaction tube 1 has a gas inlet 5 downstream of the graphite support 4 for feeding a gas inert to the reaction into the reaction tube, and a gas inlet 5 adjacent to the graphite support 4 for supplying raw material gas, transport gas, and inert gas. It is equipped with a gas exhaust port 6 for discharging the gas. A high frequency coil 7 for high frequency heating is provided outside the quartz reaction tube 1 at a location where the graphite support 4 is located.

In a gallium arsenide vapor phase growth apparatus with such a configuration,
A gallium arsenide single crystal substrate (hereinafter simply referred to as a crystal substrate) 8 is placed on a graphite support stand 4 installed in a quartz reaction tube 1 through a sample introduction port 3, and the vicinity of the crystal substrate 8 is heated by a high frequency coil 7. On the other hand, trimethylgallium, which is an organic metal raw material, and arsine, which is a raw material for arsenic, are fed into the reaction tube 1 from the reaction tube 2, thermally decomposed near the heated crystal substrate, and epitaxially grown on the surface of the crystal substrate 8. At the same time, a gas inert to the reaction is fed into the reaction tube 1 from the gas inlet 5. Therefore, the raw material gas that has passed through the reaction section near the crystal substrate is quickly discharged from the gas outlet 6 without flowing in the direction of the sample introduction port 3. At this time, not only the crystal surface of the crystal substrate 8 but also the heated graphite support 4 and the graphite support 4
Although a small amount of gallium arsenide precipitates on the reaction tube wall near the reactor, it does not precipitate and adhere to the entire downstream part of the reaction tube wall as in conventional vapor phase growth equipment. When the finished crystal substrate 8 is taken out from the sample introduction port 3, gallium arsenide does not fall onto the substrate surface.Furthermore, deposits deposited on the reaction tube wall are removed by hydrogen chloride gas without the crystal substrate being placed. Since gallium arsenide can be added and removed, there is no risk of gallium arsenide falling onto the surface of the spread plate when the crystal substrate 8 is next mounted from the sample introduction port 3. In this way, according to this embodiment, the crystal substrate It becomes possible to maintain the surface condition well.

FIG. 2 shows another embodiment of the vapor phase growth apparatus of the present invention,
Figure 3 shows a cross-sectional view of an embodiment in which gallium arsenide and aluminum arsenide can be grown.

This vapor phase growth apparatus is equipped with a quartz reaction tube 12 having a double structure of an inner tube 10 and an outer tube 11. The reason why the reaction tube 12 has a double structure is to make it easier to control the gas flow than in the embodiment shown in FIG. Quartz reaction tube 12
At the end of the inner tube 10, a reaction preform 113 is formed for introducing the raw material gas, and on the inner wall of the inner tube 10, graphite 1 to a support 14 for placing a crystal substrate are provided. There is a space 15 between the inner tube lO and the outer tube II in the inner tube wall adjacent to the downstream side of the graphite support 14.
An internal gas outlet 16 is formed which leads to an internal gas outlet 16 . Inner tube 1
The downstream end 17 of the tube 0 is connected to an inwardly protruding protrusion 18 of the outer tube as shown. Then, the inner tube and the outer outer tube were closed in sequence (internal gas (J[outlet 16
) to form a space 15. A gas inlet 19 for feeding an inert gas into the reaction is formed in the outer tube portion downstream of the protrusion r:y1s, and a gas inlet 19 for feeding an inert gas into the reaction is formed in the outer tube portion that forms the space 15. A gas outlet D 20 is formed for discharging gas. At the downstream end of the outer tube 11, a sample inlet 21 is formed for attaching a No. 1r crystal substrate and for ground formation, and a graphite support 14 is formed.
The outside of the reaction tube 12 where the
A high frequency coil 22 is provided.

In a vapor phase growth apparatus having such a configuration, the crystal substrate 23
is placed on the graphite support stand 14 through the sample introduction port 21, and the vicinity of the crystal substrate 23 is heated by the high frequency coil 22. The crystal substrate 23 is held at 600 DEG C. to 850 DEG C. by a graphite support 14 heated by high frequency induction. And gallium and ゛? Trimethyl gallium and trim'ethyle aluminum are the raw materials for Lumium.
and arsine, which is an arsenic raw material, are sent into the interior of the inner tube 10 of the reaction tube 12 from the reaction precursor [113]. The fed trimethylgallium, trimethylaluminum, and arsine (crystals) are thermally decomposed in the vicinity of I:1ff123 and precipitated as gallium, arsenic, and aluminum+1hum1ift element. At the same time, a gas inert to the reaction, in this case hydrogen, is introduced from the gas inlet 19. Therefore, the raw material gas that has passed through the reaction section near the crystal substrate flows in the direction of the sample introduction [121], passes through the internal gas discharge [116 and gas 1], and is quickly discharged from the reaction tube 12. As a result, the internal gas t
Gallium arsenide and aluminum arsenide do not adhere to the tube wall extending from the JY outlet 16 to the sample inlet 21 at all.

As a result of experiments using the vapor phase growth apparatus of this example, it was found that defects on the crystal surface (,1000f solids/cl) found in thin films formed by conventional vapor phase growth apparatuses ranged from 100 to 100.
It turned out to be less than 500 (prisoners/cl).

〔Effect of the invention〕

As is clear from the explanation in -1- below, according to the present invention, contamination of the crystal surface can be suppressed and a good crystal surface can be obtained, so the yield of semiconductor devices can be significantly improved compared to conventional vapor phase growth equipment. It becomes possible to do so.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the invention, and FIG. 2 is a sectional view showing another embodiment of the invention. 1.12...Quartz reaction tube 2.13--TV' reaction tube entry [1 3,21...4) Sample introduction L1 4.14...Graphite support stand 5.19...Gas introduction Port 6.20...Gas Ide[1 7,22...High frequency coil 8.23...Crystal group 1 to 10...Inner tube 2...Outer tube 15... ··space

Claims (1)

[Claims] (1) In a vapor phase growth apparatus equipped with a reaction tube having an inlet for supplying the raw material gas, a sample inlet for mounting and taking out the substrate, and a support stand for placing the substrate, the reaction tube is configured to supply the raw material gas. A gas inlet for feeding an inert gas into the reaction and a gas outlet for discharging the raw material gas and the inert gas are provided downstream from the support base to the sample inlet with respect to the gas flow; A vapor phase growth apparatus characterized in that crystals are not generated on the tube wall of the reaction tube between the gas outlet and the sample inlet.